Adult obesity has increased significantly in recent times. For example, recent reports estimate that about 64 percent of Americans are overweight, with more than 30 percent being obese [U.S. Food and Drug Administration, U.S. Department of Health & Human Services, Press Release, Mar. 12, 2004]. Similar reports suggest that poor diet and inactivity are poised to become the leading preventable cause of death among Americans. Thus, obesity and obesity-related disorders such as type II diabetes, hypercholesteremia, and/or metabolic syndrome (also known as syndrome X) are significant problems for modem societies [see also, Han, et al., Obesity Research, 10(9):923-931 (2002); Bonow, New England J. of Med., 348(21):2057-2058 (2003)].
Metabolic syndrome is not a disease state per se, but rather the collective presence in an individual of risk factors such as abdominal obesity, atherogenic dyslipidemia, raised blood pressure, insulin resistance, glucose intolerance, proinflammatory conditions, and prothrombotic conditions [Grundy, et al., Circulation, 109(3):433-8 (2004)]. When one or more (particularly, three or more) of such risk factors is present, the individual has an increased risk for a variety of disease states including diabetes, heart disease, and/or stroke. Individuals having metabolic syndrome are also susceptible to other conditions such as polycystic ovary syndrome, fatty liver, cholesterol gallstones, asthma, sleep disturbances, and some forms of cancer. Most practitioners consider weight reduction to be a primary “therapy” for treating metabolic syndrome. Weight reduction is also considered to be an effective therapy for treating obesity and obesity-related disorders including but not limited to type II diabetes and hypercholesteremia.
Therefore, appetite is one important regulatory pathway that can be targeted to treat obesity and obesity-related disorders [see also, Marx, Science, 299(5608):846-849 (2003)]. Several formulations capable of suppressing appetite are available commercially. Many such known appetite-suppressing formulations contain a mixture of ephedra and caffeine [Bents, Annals of Internal Medicine, 138(6):468-471(2003)]. Although appetite-suppressing formulations containing such mixtures are effective, potentially hazardous side effects are associated with ephedra administration, especially when its use is combined with stimulants such as caffeine [U.S. Food and Drug Administration, U.S. Department of Health & Human Services, Press Release, Feb. 28, 2003]. In view of the aforementioned potentially hazardous side effects, the U.S. Food and Drug Administration banned the sale of dietary supplements containing ephedra [J.S. Food and Drug Administration, U.S. Department of Health & Human Services, Press Release, Feb. 6, 2004]. Thus, safer appetite-suppressing formulations are needed.
U.S. Pat. No. 6,376,657 to Van Heerden, et al. discloses appetite-suppressing compositions containing steroidal compounds. The appetite-suppressing compositions are derived from desert succulent plants of the genera Trichocaulon and Hoodia, such as Hoodia gordonii. Similarly, International Patent Publication No. WO 03/041727 discloses compositions having appetite-suppressing activity derived from desert succulent plants of the genera Stapelia and Orbea. Such desert succulent plants are native to arid or semi-arid regions, and therefore have adapted to store water in a manner that makes them extremely difficult to propagate and cultivate. For example, such succulent plants typically have reduced leaves with a hard and heavily cutinized outer surface, which minimizes evaporation from the inner plant tissue. More specifically, Hoodia gordonii plants take nearly five years to reach maturity, produce only about 0.2 grams of fresh plant material in one month (per plant), and occupy a significant area (over about 500 square centimeters (cm2) per plant). Consequently, Hoodia gordonii plants are capable of producing only about 43 grams of fresh plant material per square meter in one year. Thus, the aforementioned plants do not provide a satisfactory source of appetite-suppressing compositions.
The Asclepiadaceae family of plants includes the Asclepias genus, as well as diverse genera such as Trichocaulon, Hoodia, Stapelia, and Orbea. Diversity among plant genera belonging to the same plant family is well-known. Such diversity is often demonstrated by the chemical compounds produced by a plant. For example, the Solanaceae plant family contains both Nicotiana tabacum(tobacco) and Lycopersicon esculentum(tomato), and tobacco plants produce nicotine whereas tomato plants do not.
Asclepias is a plant genus belonging to Asclepiadaceae comprising about 75 species of non-succulent “milkweed plants” that may contain poisonous, toxic cardiac glycosides capable of causing death in humans and livestock [U.S. Department of Agriculture, Natural Resources Conservation Service, Plant Guide, Butterfly Milkweed, Jan. 17, 2001]. Such milkweed plants are often grown as food sources for the caterpillars of several species of butterflies. The toxic cardiac glycosides accumulate in the larvae of the butterflies making the butterflies distasteful, thereby providing an effective chemical defense against predators. Compositions derived from Asclepias plants such as Asclepias tuberosa have been used to treat chest and upper respiratory infections [Physicians' Desk Reference for Herbal-Medicines, 2nd ed., 598-599 (2000)]. Although reports suggest that compositions derived from Asclepias tuberosa have anti-inflammatory and/or anti-spasmodic activity, their effectiveness in treating the aforementioned respiratory conditions has not been scientifically confirmed [Physicians' Desk Reference website, Pleurisy Root (2004)].